Sound deadening sheet material and method of manufacture



April 28, 1953 E. o. GRosKoPF 2,636,543

SOUND DEADENING SHEET MATERIAL AND METHQD OF MANUFACTURE Filed Jan. 7, 1950 @u s a.: Pfff? rmx L V524 raw rfa FL 7' A57; MTE? or Ess 70%fmva A/va CLAW/Qua? EG. Z.

IN VEN TOR. f'pw//v 0r ra Gees/(OPF,

-BY M@ ATTORNEYS Patented Apr. 28, QS

SOUND DEADENING SHEET MATERIAL AND lVIETI-IOD F MANUFACTURE Edwin Otto Groskopf, Cincinnati, Ohio, assignor to The Philip Carey Manufacturing Company, Cincinnati, Ohio, a corporation of Ohio Application .lanuary '7, 1950, Serial No. 137,477

l1 Claims.

My invention relates to pliable sound deadening sheet material for damping the sound produced by vibratile sheet metal and is particularly suitable for application to sheet metal structures such as are employed in the fabrication of metal bodies for automobile vehicles, and to a method by which such material may be made.

At present the automobile industry deadens the vibratory sound or drumming of sheet metal bodies by one of two general methods. The rst method is by the spray application of a thick coating of either an emulsion or a solvent preparation of a bituminous composition containing as a filler sand or silex (silica ilour) and sometimes containing also a limited amount of other mineral llers and of a reinforcing ber such as asbestos. These compositions are commonly referred to as spray-on deadeners. Several large automobile manufacturers now use very large amounts of such types of spray-on deadeners for application t0 the inside of the floor and side Wall panels 0f the automobile body.

The second method, which also is in extensive use by several large automobile manufacturers, employs fibrous sheet material Which is cemented or otherwise attached to the sheet metal structure which is to be sound deadened. The fibrous sheet materials used include fabrics, ielts or pads of various thicknesses, as single sheets or combinations of tWo or more layers, made from organic bers such as cotton, Wool or jute, or from glass fibers. The most extensively used material is an asphalt impregnated organic ber felt which is generally similar in character to the asphalt saturated felt used as a base for the manufacture of asphalt shingles and roll rooiings. Both methods of sound deadening, the spray-on composition and the cemented fibrous sheet, quite often are employed for different areas of the metal body of the same automobile, due to differences in the amount of sound damping required and in ease of application of the two types of material.

It has been found that some parts of the automobile body require greater deadening than others. In the case Where spray-cn deadener is used greater eiiiciency may be provided by applying a thicker layer or using a heavier composition. Where cemented brous sheets are employed the desired degree of deadening can be obtained by installing multiple layers of the material. It is known also that the degree of sound damping obtained with either method is largely dependent upon the mass elect of the 2 deadening material and to a lesser extent upon absorption by the material or the sound that is generated by the vibration of the metal sheet.

A particularly difficult problem is the sound deadenlng of the dash panel which separates the engine compartment from the body ol' the car. It is essential to reduce the transmission or" engine noise into the space occupied by the passengers and also to prevent excessive transi'er oi' heat through the dash, particularly in hot Weather'. rlhe deadenlng material 'used therefore should also be an eli'ective thermal insulation. Multiple layers oi' asphalt-impregnated ielt have quite generally been used ior deadening the dashpanel, sometimes ih combination with a pad or batt or glass libers oi' about 'LVS inch. rlne area of the dash panel requiring deadening is commonly about 9 to 'lu square reet per car. '.l'he degree 0I' sound damping obtained by the use of even as many as four layers of asphalt-impregnated i'elt combined into a board having a thickness oi 0.300 inch has been found inadequate and tests have been made with as many as eight plies 0I' such Ielt attempting to solve this problem. lncreasing the number o` plies improves the sound deadenihg emciency or the structure by increasing its mass or Weight, but also increases the cost proportionately.

It has been determined that sheet lead is a very enicient sound deadeher Ior the dash panel because its high density enables it to exert a very great mass eiect. However, sheet lead does not have suitabie physical properties to enable it to be punched and Iastened to the panel. Because it is a metal its thermal insulating properties are very pool'. BurthermOre, lead is not available commercially in the quantities that would be required and its cost is too high to be economic ror this use. My invention is directed to solving this problem by combining in a single product the essential characteristics of a sheet material that has greatly improved sound deadening emciency by reason oi' its great mass ei'ect, can be readily fabricated from available raw materials, has plability and plasticity to such a degree that it is easy to handle and install ih the car, has substantial thermal insulation value, and can be produced at a lovv cost.

Attempts to obtain the required mass eli-ect by thicker applications of spray-0n deadeners have not proved practical because the nature of these coatings involves serious problems of application, drying, cracking of the dried coating, shrinkage, loss of adhesion, brittleness at low temperatures and other dilliculties. Hot mixed mineral filled 3 asphalt rnastics have been produced in thick lslab form and experimented with for deadening the dash panel. Such a slab has greater density than the asphalt-impregnated felt structures and gives a desirable mass effect, but is not practical for use because it cannot easily be punched or fabricated, it tends to soften and iiow from the heat of the engine, it is diiiicult to lit and attach securely to the dash panel, and it becomes very brittle and fractures easily in cold weather.

My invention embodies in a fabricated sheet product the desirable characteristics of an asphalt emulsion-type spray-on sound deadener '(these qualities including mass effect, stability against now under heat, freedom from brittlenessatlow temperatures, and low cost) combined with the desirable characteristics of bitumen-impregnated felt structures (including ease of cutting and punching, pliability, plasticity that enables the panel to conform to the metal, toughness, and vthermal insulation value.

An asphalt emulsion-type spray-on deadener has been Vdeveloped and is extensively used for `spraying on the inside of the floor, trunk compartment, and rear quarter panels of the car body.

This emulsion imparts a permanent stable structure to the coalesced dried asphalt film after the Water has been removed. Fine sand is lgenerally used as the mineral nller for the spray-on deadener and this is held in suspension and stabilized by the asphalt emulsion until the material is applied to the metal by spraying. The application is mechanicallyr difficult and involves high labor cost. This type of deadener gives effective sound damping, but adeguate time and suitable ovens to evaporate the water in the spray-on deadener coating must be provided.

It is one of the objects of my invention to maire a mineral-filled emulsion deadener composition that contains a substantially increased proportion of solids and a correspondingly reduced proportion of water, while still maintaining the composition of iiuid consistency such that it may be pumped, sprayed, or spread into a uniform layer by rolls or doctor blades. The minimurssolids content of the composition should be 85 per cent by iveight and preferably is 90 per cent or more by weight. In the preferred composition ne total water content of the composition does not exceed per cent. By so increasing the solids content and reducing the water content I am enabled to achieve the further object of my `invention which is to combine the emulsioncl-.eadener composition with a 'fibrous sheet carrier, thereby producing a unitary sound deadener sheet material that has the advantages above set forth,

In carrying out my invention the emulsion- 4deadener composition is combined with one or more layers of brous sheet material. For eX- ample, a sheet of suitable bitumen-impregnatedv that it can be handled and applied in the same manner as for multi-ply felt sound deadener v,of a special character.

boards, but its overall properties in respect to weight and sound deadening effectiveness are largely determined by the thickness and composition of the emulsion-deadener lling layer or layers.

It is a further object of my invention to so combine the ingredients in the emulsion -deadener composition that this layer itself will have sufcient moisture permeability as to gradually permit the evaporation of its moisture content through the niorepervious surfacing sheet. In describing this quality I use the terms permeable and permeability This quality of perlncieability permits evaporation not only of moisture but also Aof volatile solvents with which it vmay be brought into contact.

The brous sheet carrier which I employ for combining with the emulsion-deadener must be It must be capable of being brought into contact with a water-emulsion without loss of sheet integrity or excessive loss of strength. It also must be permeable to moisture both in the form of liquid water and of water vapor. An asphaltfimpregnated felt containingbetween aboutJ 35 per cent and 95 per cent by weight (based on the unsaturated felt weight) of saturant is Isuitable although a narrower range of about i5 per cent to about 75 per cent by weightfis preferable. an asphalt-impregnated felt l containing saturant in the range above speciiied is not completely saturated and does not have all its interior void spaces filled with asphalt; it thereiore remains permeable to water vapor and to liquid water to some extent, but doesnot disintegrate or exhibit excessive loss of strength when y brought into contact with the emulsion-deadeher.

A fully saturated asphalt felt on the other hand, normally contains from per cent to 200 per cent by weight of asphalt; it therefore is substantially impermeable both to liquid water and to water vapor and will not servethe purpose of my invention. I may, however, use in place 0f asphalt-impregnated felt other permeable fibrous sheets, including woven fabrics, porous papers, non-woven cemented fibrous webs, or perforated sheets, provided they are either inherently resistant to disintegration by the action of moisture or have been so treated with -a suitable waterresistant binder or water-repellent material that they do not lose integrity of sheet structure when combined with the emulsion-deadener composition. The brous sheet may be smooth or it may be indented or embossed to increase its thickness and enhance its sound deadening effectiveness.

In making the emulsion-deadener composition for use in fabricating the new product of my 'invention, I have found it very `advantageous to Vuse a soft, ilexible, loW softening-point asphalt as this ensures that the composite panel board will be pliable and non-friabler at low temperatures. Such an asphalt is particularly suitable for use in an emulsion-deadener, but cannot be used for the same purpose if made as a hot mastic or. as a solvent cut-back composition. The latter two types of compositions are inherently more impermeable than bituminous emulsions and they also now into the pores of the brous felt to agreater extent and render it more impermeable sothatit is unsuitable for cementing to metal .with .the special adhesives commonly used inthe automobile industry for this purpose. These adhesives employ a volatile solvent Vand when inccontact with an impermeablefelt or an impervious inner layersuch as hot asphalt mastic or vasolvent cutback mastic, Vvthe solventdoes .notdiffuse and evaporate rapidly Venough to develop the required adhesion strength between the metal and the sound deadener sheet, particularly when the sheet has been applied only a short time before passage through high temperature ovens.

. In making the emulsion-deadener composition for use in my new product, my invention contemplates by the use of a suitable percentage of a bituminous emulsion and the selection of the proper screen size gradation of a heavy mineral ller such as fine sand, the production of a composition containing as high as 90 per cent by weight of solids while still maintaining the composition of a fluid consistency that is workable or pourable. 4By selection of a mineral filler of greater density than sand, such as iron oxide (powdered magnetite) or barium sulfate (powdered barytes), or by using a powdered metal such as iron lings, I have found that the solids content of the emulsion-deadener composition can be further increased, even considerably beyond 90 per cent by weight.

As a specic example of an emulsion-deadener composition that gives satisfactory results in the production of my new sandwich-type sound deadener board, the following materials are thoroughly mixed in a suitable mixer:

Pounds Static asphalt emulsion (containing approx.

50% water, 312% of bentonite and itil/2% f bitumen) 266 Kaolin clay 94 Fine graded sand 650 The static asphalt emulsion in the above formula is prepared from a suitable soft asphalt (softening point in the range 75 to 130 E), emulsified with a mineral colloid, such as bentonite, as the stabilizer for the dispersion of the asphalt particles in water. The emulsion-deadener composition as prepared for use contains about 87 per cent solids by weight, in the above example. It is of suitable consistency to be owed on a coating or combining machine in a continuous uniform layer, between two sheets of moisture-permeable felt.

I The manufacture of my new sound deadener panel may readily be carried out on any suitably equipped laminating or combining machine which has reels for supplying two or more sheets of fibrous felt continuously to a combining conveyor. Thus the sandwich-type board may be made by continuously supplying two sheets of permeable asphalt-impregnated felt, preferably indented or wafiied to the combining rolls and feeding therebetween a layer of the emulsiondeadener of regulated thickness to produce the finished board of desired caliper. When the emulsion-deadener is brought into -contact with the permeable felt some of the water content of the emulsion-deadener is absorbed by the felt and this causes the asphalt particles to ccalesce. As the water is withdrawn from the emulsion the asphalt particles act to cement the sand and clay into a solid mass and to adhere this hardened mass to the asphalt-impregnated felt. Since the water content of the emulsion-deadener is small, not exceeding 15 per cent by weight of the material as applied on the machine, there is required only a small amount of absorption and evaporation from the combined board to reduce the moisture content of the product to that which is normally present in equilibrium with atmospheric 6, moisture. The redistribution of the moisture content within the product and normal evaporation to the air may be suflicient, but for additional drying I have found it entirely practical to direct currents of forced air against the surfaces of the board on the laminating machine. The entire composite sheet being permeable to moisture, as set forth hereinabove, is preferably dried to a moisture content of ve per cent or less.

Thus I have shown diagrammatically in Figure 1, a suitable laminating or combining machine, the drawing showing a machine like that shown in Figure 1 of the Smith Patent No. 1,195,408 of August 22, 1916, and the webs of absorbent moisture-permeable, partly saturated felt being fed together with a supply therebetween of bituminous emulsion of low water content heavily loaded with nely divided mineral matter which bonds t0 the felts forming, after moisture from the emulsion has been absorbed by the felts, the residue layer in which the bituminous particles have coalesced as a result of the inversion of the emulsion, forming the sound deadening sheet material.

Figure 2 shows diagrammatically an enlarged typical cross section of the sound deadening material at the time of bonding.

Figure 3 shows diagrammatically an enlarged typical cross section of the sound deadening material after the bituminous bonding layer has coalesced and the absorption of moisture from the emulsion by the felts has caused the emulsion to invert.

As a speciiic example, by combining one layer of smooth asphalt-impregnated felt of about 0.065 inch thickness with a layer of indented (waliled) asphalt-impregnated felt of about 0.095 inch thickness, using as the lling layer in the sandwich the above described emulsion-deadener composition applied to a thickness of about 0.140 to 0.150 inch, I have produced a combined board with a thickness of about 0.300 to 0.310 inch and which weighs about 1000 grams per square foot. For comparison, a conventional sound deadener board made by combining four layers of asphaltimpregnated felt each of about 0.067 inch thickness with three layers of hot asphalt each of about 0.010 inch thickness had a caliper of about 0.300 to 0.310 inch and weighed about 500 grams per square foot. Thus, it is evident that for the same thickness my new product weighs about twice as much per square foot as the present commercial sound deadener board and has a correspondingly greater mass etlect in damping vibratory sound.

Because sand, clay and asphalt are much lower in cost than felt, my product, having superior sound deadening effectiveness, can be produced more cheaply than present commercial felt-asphalt sound deadener boards. My invention eliminates from the conventional construction two layers of expensive felt, replaced by a layer of emulsion-deadener which contains (in the dried film) about per cent by Weight of sand and clay and about 15 per cent by weight of asphalt.

As a `further example of the advantages of my invention, I have found that I can make an emulsion-deadener sandwich board of the same weight per square foot as the conventional four-ply felt and asphalt board by employing two layers of asphalt-impregnated felt each of about 0.067 inch thickness combined with a layer of emulsiondeadener of about 0.066 inch thickness. The thickness of the resulting sandwich-type board is about 0.200 inch as compared with about 0.300

7vv inch', for therfour-ply felt and asphalt board; andl they areoi vequivalent sound-1 deadeningy eiective-- ness.-V My new sandwich-type Adeadener will ac.-` complish thesame; degree of soundl deadening .at a-much lower-cost.,v

My invention is not l.limited ito. the. yparticular:- proportions ofv materials set forthv above, but-may' be'varied within fairly Wide-'limits toproduceanf improved sound deadeningapanei. minants. ofjthe. variations depend vupon.retention ofithe.V `.properties of.v high. .Weight .per i unit area: freedom.I from. any tendency for-fthe filling :layer to softenvv or extrude from between .theocover sheets underfnormal...conditions .oisheat offthe partso-f. the.:` automobile on which the. sound.- deadener. has been; applied-,10i` during the pericdwhile theiautomobilewbodyvis snbjectedto oven tem-` peratures...as. high -as 450..- 'Fg on. the production assemblyline; freedom. from brittleness atlowftemperatures; freedom from cracking, splitting# 1 or .v delaminating.; and 'maintenance of .pliability, plasticity-.and l,toughness such that I with. `changes oftemperaturefthe ysheetdces not tend to warpv the intermediate layer of the sandwich. Ih'ave found that'thefemulsion-deadener should 'contain not-less than F10-:per- .cent byI weight ofA 'lnelyr` dl*- videdmineral matter (includingsandg clayandy other mineral n-llers), notle'ssthan l0 percent byweight of asphalt.k tar or other bitumen havin-gaiowfsoftening point .(inthe-range from-75 to4 170 FJ, c.-.stabilizer for the asphalt emulsion to prevent flow of the dried film: under heat such forexample, as, about 450- andA not more than percent byweiaht of water.

As -to the.V permeablebrous sheets used 4in producing; the sandwichftype. deadener,` these. cani vary in thickness. Organiciiberffeltis'produced commerciallyintheI range from; about 0.0201to- 0.l00 inch thickness.' nsncaking myrnew-product Imay use a. brousfsheetas thinv as '0:010 inch providedthe sheet ils-adequately strong for conveyinq the-fabr-icatedwboard overfth'e combining machine and handling. andapplication` of the finished sound deadenerV board.y Normally, I emrploy'feltsheets in the range of thickness from.

0.030to 0.070 inch in themanuactureof this product.' The thickness. of theemulsionfdead.- ener filling layer may Arange between about ..030 and .0.500. inch, but usually willbeemployed in therange between 0.060 and. 0.300inch to afford the. optimum combination oft propertiesofv the product.

Whilefbroadly my invention comprises asandwich .felt struct-urehaving,r a, pliable plastic Eller layercomposedof emulsiied bituminous materialv binding a. high proportion of finely divided mineral matter, it is preferable that for; maximum effectiveness as a vsound deadenerV and. for mini: mum; cost theV fillerl vlayer gshould, be. of greaterl thick-ness than the layers of fibrous sheet vmate@A rialy between which the `ller :materialrisfdisposed-. Thus,t the full yadvantageswf.my inyentiongwill not be realized unless the. ller layer is of suffi-'-v cient thickness ,te be@ functionally. effective: by 116550113 its fmassgeffect. I haverfoundethatxfon Thedeter-y effectiyasoundadamping .the .finished'-gsheet's1iould:

bernot.l less than .060 inch in thickness:`

Havingt thus describedjby invention, whatlv claiml .as newA f and desires. to.; secure by Letters.`

Patent is:

1.. Sound deadeninglsheet. material having rthe following desirable characteristics; ease of cute.V tingand punching, pliability and plasticity which.,v

enables the materialto be shaped to conform to.

` thek shape Vof metal.: parts,v toughness, thermalxin.-

sulation .1Value, mass eiect,. stability against nowi.

under heat f and freedom from `brittleness at low. temperatures; and. consisting of a sandwich have ingasurface plies of an absorbent '.moistureeper.-

meable, partly saturated .felt .containing from 45,'

izo-@75%y of bituminous saturant based. onv the-v weight of the dry. felt; and anintermediatebond'e ing,rv` layer adhering to. the adjacent..surfaces-`ot` said plies. of felt; said;` bondingplayer.-A being ther residue off-a bituminous emulsion ',comprising, by;

. in. claimt-l wherein the. finely divided `mineral.

matter comprises as its essential'maiorcompofl nent, finely graded'sand.

3. Sound deadenlng sheet material as set forth in claim ll wherein the' nnelyv divided mineral; matter .consists `in about 1.13; per cent. kaolin, clay and 87 per cent finely gladedsand.

Sounddeadening .sheet material asset forthv in claiinl wherein thethickness of thecombinedA board is from about 0.300 to 0.310 inch and which weighs about 1000 arms. per square foot.

5.` Sound d-eadeningsheet material asset forth in clairn l ywhereinthebituminous sa-turanti for. the: partial saturation ot theffelthas a; melting point of fromrl5" s011309 F.

6. A method of producing acomposi'te soundl deadeninggsheet material consisting: of conyeyingf betweenj spacedV rollers two sheetsoffabsorbent; moisture-permeableffelted; fabric containingfr'om 45 to-75% by weight :of bituminousI saturant,:sup--y plying, betweenf said .spaced Vsheets. a layert of fay fluid; emulsiolfi.-.lleadenerr composition. con'iprisingxr at least 70 per cent by weightof-finelydivided mineralamatter; andi not less than: about lOIper cent of bitumen and. not more thanabout vliiper cent jeff-waters. maintainingl said sheets and saidY emuliondeadener composition in contact 'wll'ereA by apart ofithewater ofrthelernulsion is absorbed alescenoe ofthe asphalt; particles ci saidfiasph'alt emulsion, saidlcoalesced .asphalt 'particles binde, ingsaidfinely divided mineral matter into. aisolid mass and` adheringY said massseourely tosaidtabe sorbent. moisture-permeablesheets and aindry-f. ingsa-id compositen sheet materialA to;reduceits; moisturecontent lto about fper-.entor-less weight.

'7; A method.v as set forthinclairh `6*,wl1ierein the bituminous saturant hasv a.. melting. point-,of nomic? to 1302 s'.

8. AV method as set forth in claim-6 wherein'the' nely.l divided mineralv matter.comprises--asgits essential major component nely gradealsandzi 9.Y A methode-sect Vforth-in claim dwheren the. finely` divided mineral matter is about lv.'l'3rpe1: .cent kaolin; clay and S7 per cent.. iinely graded sand;

10.A-method asset forthinnclaim wherein the thickness of :i the felt; .is about i .067 Finch'in.

tbiQkness-fand-thefthicknessfoffthe'bondingllayee is about .066 inch in thickness, making a combined thickness of about .200 inch.

11. A method of producing a composite sound deadening sheet material consisting of conveying between spaced rollers two sheets of felted fabric partially saturated with bitumen only to the point where said :fabric remains moisture-permeable, supplying between said spaced sheets a layer of a. fluid emulsion deadening composition comprising at least about 70 per cent by weight of finely divided mineral matter, about 10 per cent of bitumen and about 15 per cent of water, maintaining said sheets and said emulsion deadener composition in contact whereby sufficient water from the emulsion is absorbed by said felted sheets and said withdrawal of water causes coalescence of the asphalt particles of said asphalt emulsion, said coalesced asphalt particles binding said finely divided mineral matter into a solid mass 10 and adhering said mass securely to said absorbent, moisture-permeable sheets, and air drying said composite sheet material to reduce its moisture content.

5 EDWIN O'ITO GROSKOPF.

References Cited in the le of this patent UNITED STATES PATENTS lo Number Name Date 1,195,408 Smith Aug. 22, 1916 2,008,654 Clarvoe July 16, 1935 2,057,251 Seigle Oct. 13, 1936 2,180,305 Groskopf Nov. 14, 1939 l5 FOREIGN PATENTS Number Country Date 513,255 Great Britain Oct. 9, 1939 

6. A METHOD OF PRODUCING A COMPOSITE SOUND DEADENING SHEET MATERIAL CONSISTING OF CONVEYING BETWEEN SPACED ROLLERS TWO SHEETS OF ABSORBENT, MOISTURE-PERMEABLE FELTED FABRIC CONTAINING FROM 45 TO 75% BY WEIGHT OF BITUMINOUS SATURANT, SUPPLYING BETWEEN SAID SPACED SHEETS A LAYER OF A FLUID EMULSION-DEADENER COMPOSITION COMPRISING AT LEAST 70 PER CENT BY WEIGHT OF FINELY DIVIDED MINEAL MATTER, AND NOT LESS THAN ABOUT 10 PER CENT OF BITUMEN AND NOT MORE THAN ABOUT 15 PER CENT OF WATER, MAINTAINING SAID SHEETS AND SAID EMULSION-DEADENER COMPOSITION IN CONTACT WHEREBY A PART OF THE WATER OF THE EMULSION IS ABSORNED BY SAID ABSORBENT, MOISTURE-PERMEABLE FELTED SHEETS AND SAID WITHDRAWAL OF WATER CAUSES COALESCENCE OF THE ASPHALT PARTICLES OF SAID ASPHALT EMULSION, SAID COALESCED ASPHALT PARTICLES BINDING SAID FINELY DIVIDED MINERAL MATTER INTO A SOLID MASS AND ADHERING SAID MASS SECURELY TO SAID ABSORBENT, MOISTURE-PERMEABLE SHEETS,AND AIR DRYING SAID COMPOSITE SHEET MATERIAL TO REDUCE ITS MOISTURE CONTENT TO ABOUT 5 PER CENT OR LESS BY WEIGHT. 